Chevrolet 10 Series 1968, Service Manual

Page: 464 / 713

SECTION 7
TRUCK CLUTCHES & TRANSM ISSIONS
CONTENTS OF THIS SECTION
Page
Clutch C o n t r o ls ....................................................................... 7-1
C lu tch es.................................................................................... 7-8
Manual T ra n s m is s io n s .......................................................... 7-12
Manual Transm ission C o n t r o l s .......................................... 7-23
Page
Aluminum P o w e r g l i d e .......................................................... 7-36
Turbo H y d r a -M a tic ................................................................ 7-43
Special T o o l s .......................................................................... 7-52
CLUTCH CONTROLS
INDEX
Page
General D e s c r ip t io n ............................................................. .... 7-1
Maintenance and A d ju s tm e n ts ............................................. .... 7-3
Clutch F ree Pedal T ra v e l Adjustment (Mechanical) . . 7-3
Insufficient Clutch R e l e a s e .......................................... .... 7-3
Clutch Pedal Adjustment (H y d r a u lic )............................. .... 7-3
Clutch Pedal Total T r a v e l .......................................... .... 7-4
Page
Clutch Pedal F ree T ra v e l A d ju s tm e n t...................... .....7-4
Clutch Pedal (A ll Except T ilt C a b )................................ .....7-4
T ilt Cab Clutch L in k a g e ................................................... .....7-4
Slave C y l i n d e r ................................................................... .....7-5
Clutch Cross S h a ft............................................................. .....7-6
GENERAL DESCRIPTION
The operating controls for trucks are either mechan­
ical or hydraulic. The mechanical linkage (used on
6 cylinder and V -8 engine equipped vehicles except " L "
and " T " Models) consists of pendant type pedal, return
spring, pedal push rod, cross-shaft, fork push rod, clutch
fork and throwout bearing (fig. 1). The pedal push rod is
routed vertically, inside the cab, from the pedal lever
down through a seal boot on the toe pan, to the cross­
shaft lever. When the clutch pedal is depressed, the
pedal pull or push rod moves upward rotating the cross­
shaft, pushing the fork push rod rearward, and pivoting
the clutch fork to move the throwout bearing against the
clutch release fingers and releasing the clutch.
The Step Van uses mechanical linkage activated by a
floor pedal mounted through a pivot shaft on a frame
bracket (fig. 2). A pull rod connects the pedal to the
cross-shaft to activate the clutch as before.
The hydraulic controls consist of pedal, pedal push rod,
main cylinder, tubing, slave cylinder, fork push rod,
clutch fork and throwout bearing.
When the clutch pedal is depressed, brake fluid is
forced from the main cylinder into the slave cylinder
(fig. 3) moving the push rod against the clutch fork to re­
lease the clutch as before. When the pedal is released,
the clutch fork return spring forces fluid from the slave
cylinder back to the master cylinder,
A fitting is provided on the slave cylinder for bleeding
air from the system as is done with hydralic brakes.
The fluid level should be maintained approximately 1/2"
below the top of master cylinder reservoir.
On 366 cu. in. and Diesel vehicles the clutch release
bearing is moved by a yoke attached to a shaft through the
transmission half of the clutch housing (fig. 4). The hy­
draulic slave cylinder pushes a lever attached at the end
of the throwout yoke shaft, rotating the shaft and yoke and
moving the throwout bearing against release fingers of
clutch assembly.
On vehicles equipped with a yoke and shaft type release
lever, the grease cup (attached by hose to release bear­
ing) is filled with a graphite type grease and should be
turned one-turn each 1,000 miles and refilled each 6,000
miles.
CHEVROLET TRUCK SERVICE MANUAL